Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/52—Manufacture of steel in electric furnaces
  • C21C5/5229—Manufacture of steel in electric furnaces in a direct current [DC] electric arc furnace
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D11/00—Arrangement of elements for electric heating in or on furnaces
  • F27D11/08—Heating by electric discharge, e.g. arc discharge
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B7/00—Heating by electric discharge
  • H05B7/02—Details
  • H05B7/06—Electrodes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the invention relates to a method and a device for melting metallic materials in a direct current arc furnace according to the preambles of claims 1 and 2.
• the power supply to the DC arc furnaces is effected by electrodes connected to the energy station, which are usually arranged on support arms. The current is fed back to the same energy station.
• the forces acting on the weld pool during operation of the arc furnace are directed perpendicular to the electromagnetic field lines and cause a bath movement which is directed from the outside against the axis of the electrode projecting in the bath.
• the molten bath flow has a direct negative effect on the electrode face.
• the object of the invention is to provide a direct current arc furnace which, with a simple structure and with unchanged melting capacity, has less wear on the refractory lining of the furnace and the positive electrodes.
• the invention makes use of the property of such ceramic insulating materials, the specific electrical resistance of which decreases at high temperatures (Hütte, 5th edition, lafel 110).
• the positive electrode is arranged between the vessel jacket and the refractory lining. This means that the positive electrode is no longer exposed to the melt and thus no longer exposed to chemical aggressiveness, thermal as well as erosive stress.
• the user has a relatively high degree of freedom in the selection of the materials of the positive electrode.
• the refractory lining arranged in front of the positive electrode is exposed to high temperatures due to the contact of the melt, so that there is a low specific electrical resistance.
• the refractory lining in the area of the positive electrode must be heated in order to reduce the specific electrical resistance. This preheating of the furnace vessel can also be used to reduce the thermal shock effect when using cooled vessels.
• the positive electrode is in direct contact with the vessel jacket.
• This arrangement has the advantage that the current feedback can attack anywhere on a metallic part of the vessel. In the case of ladle ovens, the suspension or the bottom of the vessel are ideal. In the latter case, appropriate contact plates must be provided in the respective treatment stations.
• the positive electrode is designed in a ring shape.
• the following measures are provided for centering the arc between the negative electrode and the melt: Contrary to the blowing effect of the electromagnetic wind, the mass distribution of the electrode is designed. This is done either by changing the Cross section of the positive electrode or caused by interruptions in the electrode ring. The larger electrode mass is arranged on the energy supply and supply side of the furnace. This measure prevents the arc from deflecting. The consequence of the centrally burning arc is an even load on the refractory lining.
• an electrical insulating layer is provided between the metallic vessel jacket and the refractory lining.
• the electrical current flowing through the metallic vessel jacket is forced through the insulating layer to flow exclusively from the positive electrode to the contact jaws. This prevents leakage currents that could lead to local overheating of the refractory lining.
• a material is proposed as insulation which, in addition to the lack of electrical conductivity, has sufficient thermal conductivity. Mica, zirconium dioxide or similar substances can be used as materials.
• the thermal conductivity of the insulating layer allows the required degree of heat dissipation without the disadvantage of the possibility of reflux currents.
• the insulating layer is guided over the edge of the furnace vessel in order to prevent that faulty currents occur due to material flowing over the edge of the vessel.
• Fig. 2 shows a positive electrode ring with a variable cross section
• Fig. 3 shows an electrode ring with interruptions.
• FIG. 1 shows the section through the ladle furnace 10 with the negative electrode 21, which projects into the pot-shaped vessel 13 filled with melt 40.
• the vessel 13 has a metallic vessel jacket 11, a refractory lining 12 and an insulating layer 30 between the vessel jacket and the refractory clothing.
• the insulating layer 30 is not electrically conductive. In the upper region of the pan, the insulating layer 30 is guided over the upper jacket edge 31 of the furnace.
• the arc 23 burns between the negative electrode 21 and the molten bath 40.
• the electrical current is supplied to the negative electrode 21 via the current supply 24 and is removed again from the positive electrodes 22 via the current discharge 25.
• the positive electrodes 22 are formed from the electroconductive refractory material 22 which is arranged between the vessel jacket 11 and the refractory clothing 12.
• the electrical current is returned from the positive electrode 22 via the metallic vessel jacket 11.
• outwardly facing elements 16 are provided for power dissipation. In an embodiment, these face outward Elements 16 formed as vessel feet 14.
• the positive electrode 22 is annular and is arranged above the bottom of the vessel.
• Figure 2 shows a section A-A through the vessel.
• the power supply 24 and the power dissipation 25 are shown schematically.
• the annular electrode 22 is shown between the furnace shell 11 and the refractory material 12.
• the ring 22 has a different cross section, the larger cross section being arranged on the side of the furnace on which the current is fed in and discharged.
• the negative electrode 21 is shown in the center of the furnace.
• FIG. 3 shows the same elements as FIG. 2 with a ring 22 which has interruptions 26 which are lined with refractory material 12 and are separated from the vessel jacket 11 by the insulating layer 30. Outside the interruptions 26, the ring 22 has a uniform cross section.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Vertical, Hearth, Or Arc Furnaces (AREA)
• Furnace Details (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6354871

Family Applications (1)

Country Status (5)

Cited By (2)

Families Citing this family (1)

Citations (12)

Family Cites Families (3)

• 1988
  • 1988-05-18 DE DE3817381A patent/DE3817381A1/de active Granted
• 1989
  • 1989-05-17 WO PCT/DE1989/000317 patent/WO1989011774A1/de active IP Right Grant
  • 1989-05-17 EP EP89905638A patent/EP0414759B1/de not_active Expired - Lifetime
  • 1989-05-17 AU AU35644/89A patent/AU3564489A/en not_active Abandoned
• 1990
  • 1990-01-17 DK DK013790A patent/DK13790D0/da not_active Application Discontinuation

Patent Citations (12)

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